Air filtration systems are used in many situations to purge unwanted substances from the air. Such filtration systems generally exist in a variety of forms, depending upon their function.
One type of air filtration system in common use, e.g., in laboratories, comprises a fumehood, fumehood is a protected enclosure for isolating a benchtop workspace from the ambient air of a laboratory, in order that dangerous substances may be handled safely within the fumehood without endangering nearby personnel.
Fumehoods may be ducted or ductless. With a ducted fumehood, the exhaust air from the fumehood is directed into building ductwork which leads to the outside atmosphere, with a filter being disposed intermediate the ductwork between the fumehood and the outside atmosphere. With a ductless fumehood, the exhaust air from the fumehood is directed into a filter which is attached directly to the fumehood, with the filter purging hazardous substances from the exhaust air before the exhaust air is directed back into the ambient air of the laboratory.
Ducted fumehoods offer certain advantages, e.g., multiple fumehoods can be exhausted through a single filter, their fixed location (a consequence of the fixed ductwork within a building) make them easy to oversee and administer, etc. However, ducted fumehoods also suffer from the disadvantage that the ambient air of the laboratory is exhausted through the fumehood to the outside atmosphere. As a result, heated air is lost from the laboratory during the winter, and cooled air is lost from the laboratory during the summer, thereby driving up energy costs. Ductless fumehoods do not suffer from this disadvantage, since they return the filtered exhaust air back to the ambient air of the laboratory. However, ductless fumehoods suffer from the disadvantage that each fumehood requires its own filter, which can complicate logistical issues such as filter monitoring, filter replacement, etc.
The present invention is directed to ducted fumehoods, and more particularly to a novel method and apparatus for operating ducted fumehoods with increased energy efficiency.